1. Field of the Invention
The invention relates to a particle beam optical apparatus with a specimen holder which comprises a housing which is movable relative to the apparatus in first and second, mutually perpendicular directions, and a rod-shaped specimen support for supporting the specimen, which support is accommodated in the tubular housing and is movable in a third direction perpendicularly to the first and the second directions, said specimen support being supported, at the end thereof facing the optical axis of the apparatus, in a V-groove whose groove direction is the third direction.
The invention also relates to a specimen holder for such a particle beam optical apparatus.
2. Description of the Related Art
A specimen support of this kind is known from German Offenlegungsschrift (published Patent Application) DE 35 46 095.
Generally speaking, specimen supports must be capable of moving the specimen in three directions: the direction of the particle beam (the z-axis), the direction of the axis of the specimen support of the specimen holder (the x-axis), and the direction perpendicular to said two axes (the y-axis).
In the cited Patent Appliction the motions in the y-direction and the z-direction are realised by tilting the housing about a ball joint forming part of the housing. Because the axis of this tilt is situated outside the optical axis of the particle beam optical instrument (and hence outside the specimen), this tilt causes a displacement of the specimen in the y-direction and/or the z-direction. In this specimen holder it is also possible to rotate the specimen about the x-axis. To this end, the drive for this rotation is connected to the exterior of the housing via a bellows. The object is to achieve a torsion-resistant transmission which does not impede said tilting motions.
The displacement of the specimen support in the x-direction is guided by a V-groove in the ball forming pan of the ball joint. For displacement in the x-direction there is provided a specimen support displacement device which operates against the ambient air pressure acting on the specimen support. The cited Patent Application does not disclose how the vacuum seal between the specimen support and the housing is realised. Generally speaking, this type of seal is customarily realised by means of an O-ring between the specimen support and the housing. For accurately defined and accurately reproducible displacements, O-rings have some drawbacks: some force is required to overcome the initial friction at the start of motion of the O-ring and the material of the O-ring always exhibits some relaxation, so that the initial x-position of the specimen support is lost.